1. Field of the Invention
The present invention relates to the preparation of m-aminophenols from resorcinol. More specifically, the present invention relates to the preparation of m-aminophenols by reacting anhydrous amine compounds selected from ammonia, primary amines or secondary amines with resorcinol in an organic solvent in the presence of certain silica alumina catalysts. In particular, the present invention relates to the preparation of the compound m-aminophenol by reacting anhydrous ammonia and resorcinol in an organic solvent in the presence of a natural or synthetic silica alumina catalyst.
2. Background of the Invention
The family of m-aminophenol compounds are well known and well reported in the literature. These compounds are useful as intermediates for preparing dyes, pharmaceuticals, resins and agrichemicals. More recently m-aminophenol compounds, particularly m-aminophenol itself, have found application in the preparation of high performance polymers, particularly in the preparation of intermediates for high performance fibers.
The most well known process for preparing aminophenols is by reacting resorcinol with an aminating agent selected from ammonia, primary amines and secondary amines. The compound m-aminophenol is most commonly prepared by reacting resorcinol with ammonia. The amination of resorcinol with aminating agents selected from ammonia, primary amines and secondary amines is well documented and is the subject of many patents and patent applications.
All of the methods comprise reacting resorcinol with the amine, however, there are many different variations of the reaction. For example, it is well known to react resorcinol with the amine in an aqueous medium. This is undesirable because of the necessity of stripping the water with a concomitant loss of product. In addition, the stability of m-aminophenol in aqueous mother liquors for recycle has been erratic. It has also been suggested to run the amination in various solvents with or without the use of various catalysts. Some of these methods have been somewhat successful, however, they suffer from one or more different drawbacks. For example, some catalysts are very expensive. Some catalysts cannot be recycled without being regenerated and some are difficult to separate from the reaction mixture. Some of the other deficiencies associated with the prior art processes include low conversion of resorcinol per pass, poor selectivity in the conversion to aminophenol with too high conversion to m-phenylenediamines, long reaction times and difficulty in isolating and/or purifying the m-aminophenol.
Accordingly, it is an object of this invention to provide an improved method for aminating resorcinol with ammonia, a primary amine or a secondary amine. It is a further object of this invention to provide a process for reacting resorcinol with ammonia, a primary amine or a secondary amine that combines high conversion of resorcinol to aminophenol compound with low amounts of m-phenylenediamine by-products and which does not suffer from the other drawbacks of the prior art processes for reacting resorcinol with amines.